Lonergan is a surname. Notable people with the surname include:

• Andrew Lonergan (born 1983), English (soccer) football goalkeeper
• Arthur Lonergan (1906–1989), American art director
• Augustine Lonergan (1874–1947), US Representative from Connecticut
• Bernard Lonergan, (1904–1984), Canadian Jesuit priest, philosopher-theologian, economist
• Dan Lonergan, Australian sports commentator and writer
• Dean Lonergan, New Zealand rugby league player and events promoter
• Jennifer Lonergan, Canadian educator and nonprofit business executive
• John Lonergan (1839–1902), American military personnel; Union Army captain in the American Civil War
• John Lonergan (artist) (c. 1895–1969), American visual artist
• Julia Lonergan (born 1961), Australian judge
• Kate Lonergan (born 1962), English actress
• Kenneth Lonergan (born 1962), New York playwright, screenwriter, and director
• Lenore Lonergan (1928–1987), stage and film actress during the 1930s and 1940s
• Lloyd Lonergan (1870–1937), New York scenario and screenwriter
• Mike Lonergan, American basketball player, coach
• Richard Lonergan (1900–1925), American underworld figure and labor racketeer
• Sam Lonergan (born 1987), Australian Football player, Woodville-West Torrens coach
• Tom Lonergan (Australian footballer) (born 1984), former Australian rules footballer
• Tom and Eileen Lonergan, Peace Corps volunteers who went missing in 1998, presumed dead
• Walter Lonergan (1885–1958), second baseman in Major League Baseball